LDAP query to Active Directory

Hi all!

I'm trying to write an LDAP query to pull users from AD who are
members of a particular group.  I'm using the 'memberOf' attribute,
which according to ADSI Edit, is set correctly for the users in
question.  My query is quite simple:

(memberOf=CN=SVN-users,OU=Distribution
Groups,OU=MyBusiness,DC=<domain>,DC=com)

but it does not return all the users!  Running a query with ldapsearch
(sorry, I'm sort of a Linux guy) :) only returns four users but the
group has many more members.

I've also perused the LDAP using ldp.exe and I find that only the same
users show as having the memberOf attribute set at all.  This is true
of ALL groups, not just the SVN-users group above (i.e. most users
don't have memberOf set AT ALL).  Why is this?

Can anybody ****ne some light on this for me?  Why does ADSI Edit show
the attribute as set, but ldp.exe does not??

PS - I'm not married to using the memberOf attribute, if there's a
better way, please let me know!

Thanks in advance for any help!